His Brother's Keeper
by Kaelir of Lorien
Summary: Mycroft remembered the first time he had been forced to pull John aside and explain. It was obvious that no one had warned the doctor that the addiction came with a higher price, when Sherlock's control floundered and the spark of his restraint went out, leaving him in darkness.
1. Part I: Recollection

**Author's Note: **I've been wanting to explore Mycroft's character again, and it occurred to me that the scene at the morgue between Sherlock and his brother in "A Scandal in Belgravia" (and Mycroft's subsequent phone call to John) implies a lot more than we ever really hear in detail. When _did_ John find out that Sherlock has his 'danger nights'?

Also features a rather puzzled Mycroft, who I think, even at the end of season two, is still surprised by the unwavering loyalty and raw strength of Doctor John Watson.

**Many happy readings, and any thoughts you could leave are always, _always _appreciated. :)**

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**His Brother's Keeper**

_Part I: Recollection_

"Just the one."

Mycroft held out the single temptation between gloved thumb and forefinger, his glance roaming carefully between it and his brother. He waited.

"Why?" Sherlock's tone was sharp, verging on suspicious.

Irony served as well as anything to mask Mycroft's intentions. "Merry Christmas."

Sherlock responded with a sound of dark amusement as he reached for the cigarette, and Mycroft looked down, searching for the silver lighter in his pocket and taking advantage of the shadows on his face to re-establish his semblance of neutrality. He didn't think his expression had slipped, but he was not about to take chances. One didn't take chances with Sherlock.

He feigned composure, even complacency, during the next few minutes, watching as his brother released slow breaths of smoke into the cold, sharp air of the hospital hallway in between words. Their voices, soft and equally cold, echoed in the stillness, and he wondered, not for the first time, how they could possibly be so alike and yet forever on opposite sides of the same vast plane. Brothers, striving against each other for meaningless dominance, burying true emotion under a lead blanket of petty feuding and unsubtle resentment. The thought had crossed Mycroft's mind, once, that Sherlock, for all his faults, might have at one time been a reflection of what his older brother could have become, had Mycroft chosen a less worldly path to walk. Pointless musings, in the end.

Sherlock turned on his heel a moment later, carelessly flicking a sprinkle of ash from the cigarette, the angle of which was oddly delicate between his fingers. Mycroft knew that the conversation had been nearly over, though; they could only stand so much of each other's presence. He raised his chin slightly as his brother's unexpected "Merry Christmas, Mycroft" echoed back down the length of the dim hallway.

But that was Sherlock, after all. To expect the unexpected was not the most ideal method of dealing with him, but it was as close as anyone could get.

Mycroft frowned. Anyone, that is, except John Watson.

He waited until the door had swung shut behind Sherlock, but no longer, before quickly pulling his mobile from his jacket pocket. Mycroft had many phone numbers on speed-dial, but John's was one of the few he had also taken the time to memorise thoroughly.

Brows drawn low, he contemplated that for a moment as he listened to the dial-tone on the other end of the phone. John Watson. Doctor, ex-soldier, moral man, stubborn, firmly planted in reality. Average, in all ways but one: He was the friend – yes, _friend_ – of Sherlock Holmes, and that terribly strange happening still puzzled Mycroft beyond belief. He rarely put events down to coincidence, but nor did he believe in that extraordinary human concoction known as fate. John's place in the life story of Sherlock seemed to be hanging somewhere in between the two, which was, to Mycroft's precise and well-organised mind, exceedingly presumptuous of it.

"He's on his way; have you found anything?"

"_No. Did he take the cigarette?_"

Mycroft could hear the barely-concealed agitation in John's voice, and let out a resigned breath of an answer. "Yes."

"_Shit,_" John said softly, and right at the moment, Mycroft could hardly have agreed more.

It was not the first time this had happened, and he knew it would not be the last. Sherlock was a man of keen intelligence and remarkable discipline, but he was also a man of few virtues and many vices, and it was on this latter score that Mycroft's thought was now bent; for he knew, both through instinct and the evidence of his own senses, that his brother's self-control was teetering on the breaking point. It would take very little to send him over the edge tonight.

Which was, he mused, all the more reason why John Watson had quite suddenly become the weight that was anchoring Sherlock, the single strong point that would not yield, however reluctant John was to play the part. Even in the face of Sherlock at his most unmanageable, the doctor's loyalty remained firm. He would weather the storm, he would _not_ break, and he was bound and determined that Sherlock would not falter, either. Mycroft knew the power of loyalty, but in the case of John Watson, he found himself still at something of a loss. The doctor was, in many ways, still a mystery to him after all this time – a strange combination of emotion and common sense, of confusion and fearlessness, a melding of the ordinary and the extraordinary.

He remembered, with a slight burning of distaste, the first time he had been forced to pull John aside and explain to him the matters that Sherlock had not bothered (or conveniently forgotten) to mention: the narcotics, or rather, the desperation that drove him to them. John had been aware from the start that his flatmate kept a number of peculiar habits, nicotine patches being one of them, but it was just as obvious that no one had warned him that the addiction came with a higher price, when Sherlock's control floundered and the spark of his restraint went out, leaving him in darkness.

For there was darkness in Sherlock. He had never actively tried to hide it, but Mycroft suspected that John, still full of wonderment at the brilliance if eccentricity of his companion, did not care to look too closely for it.

It was Inspector Lestrade who made the call, though, at quarter to midnight after a day that had seen a fine sprinkling of February snow and far too many headaches for Mycroft to imagine that his mobile ringing shrilly at this hour could portend anything but mild disaster. He pressed his lips together and answered it.

"Yes?"

"_We might have a bit of a problem,_" came Lestrade's voice immediately, tensely, "_and, yeah, its name is Sherlock._"

Wearily, Mycroft closed his eyes and massaged a hand over his temple. "What's he done this time and when should I start worrying about it? Is tomorrow soon enough?"

"_I don't think we've _got_ till tomorrow. I'm not worried about what he's done, more like what he might do. He's got that – OK, you know that case he's been obsessing about for the past two days? The Buckley one, yeah. Well, it's not going too – it's not going at all anymore, actually._"

Something in the Inspector's tone caused Mycroft to snap his eyes open again. "Meaning what, exactly?" he asked, brow furrowed as he began to anticipate the answer. "Am I to understand that my brother did not bring this one to a successful conclusion?"

"_Nope. Bastard got one second ahead of us and jumped right off the Hungerford about an hour ago. Took two bystanders with him, too – shot – when they tried to move in. We got the body, God knows it's not much help to anyone now._"

This time, Mycroft remained quiet, pacing an agitated half-circle toward the darkened window of his study and staring out into the night, through which he could see tiny cold flakes still drifting. He had no particular like or dislike of snow, but its presence certainly did add an aura of gloom to the already unpromising circumstances.

Lestrade apparently took his silence as agreement, for he went on tersely, "_Anyway, Sherlock's got that look – that sort of vacant one, you know – and I don't think he's gonna hold out much longer._" A pause, eloquent in its implications. "_I'm on duty tonight. Someone really needs to be there_."

The lines on Mycroft's forehead deepened. "He has Doctor Watson – "

"_Yeah, but I don't think John really gets it, yet. He's still working Sherlock out._"

"How long has it been?"

"_Since they – oh, right, since the last time? I'd say a month and a half, at least. I think it was that thing in Kent just after Christmas that set him off._"

A few quick calculations ran through Mycroft's head, and his grip on his phone tightened unconsciously. Too long. There were cycles to these things, he had come to realise over many years, even if they were only visible in retrospect. It was the slow building up of pressure, the minute stress fractures in Sherlock's mind that were blatantly ignored until they broke apart all at once in a fit of frustration, and then Sherlock would try to lose himself, drown his overactive mind in a pool of artificial numbness.

"How bad is he?" he asked quietly.

"_I've seen him worse, but I've seen a hell of a lot better, too._"

A number of choice words, all short and none of them polite, occurred to Mycroft at this point, but he said none of them aloud. Instead, he turned abruptly on his heel and walked rapidly towards the door, his eyes and mouth set stone-like in his face.

"In that case, I'd better let Doctor Watson know the sort of night he's in for."

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**So, this became longer than I meant it to. I, therefore, as the sole power behind this story, can leave you in suspense!**

**On a brighter note, reviews just make my day. :)**


	2. Part II: Expediency

**Author's Note:** Many kind and sincere thanks to all those who have left their thoughts so far, especially eohippus and Esther Kirkland. I have, I believe, responded to everyone who signed their name, but do let me know if I haven't! Reviews do mean terribly much to me, so keep them coming! :)

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_Part II: Expediency_

There were still a few lone, tiny flakes drifting through the air, confetti-like crystals looking as though each had been created under a minute flower press, when Mycroft stepped onto the sidewalk in front of 221 Baker Street. He glanced upward, once, to the sitting room window of his brother's flat, where he could see the warm glow of at least one light, possibly two, spilling out into the night. The third floor window, however, was dark. John Watson was either asleep (unlikely; he was not unintelligent) or he had come to the conclusion, however vague, that something was indeed wrong, and had made the (intelligent) decision to stay downstairs.

With very little expression on his face, Mycroft extracted the necessary key from his pocket and, after testing the door, let himself in. He was not particularly quiet about it, and expected the landlady to come bustling out of her own rooms at any moment once the door had close again with a snap behind him – but she didn't.

All was very quiet. Mycroft frowned, considering that something of a worrisome sign.

He let out a low breath and mounted the stairs with a quicker step than usual, the sounds echoing dully as they met the bamboo-papered walls of the stairwell. Anxiety pushed a little at the boundaries of his mental discipline, but he forced it away again with his usual efficiency. It was foolish to deny that he was concerned, but concern was not something he would ever allow to overwhelm him to the point where he could not act on its object.

Low voices met his ears as he reached the second landing, and though they were muffled behind the closed door of the flat, Mycroft could pick out the two speakers without even a moment's pause. Good. Doctor Watson was still awake. He rapped sharply on the door with the back of his hand.

It was well after midnight now, and when John pulled open the door, Mycroft could see both the time and the stress of the past couple of days showing in the shadows under his eyes. The doctor's brow furrowed as he blinked and seemed to come to grips with the fact that Sherlock's elder brother was standing outside the flat. His mouth opened.

"This is – "

"I thought it best not to announce my arrival beforehand," Mycroft interrupted him smoothly, though a bite of impatience edged its way into his voice before he could prevent it; "it might have complicated matters." He gave John a pointed look. "Where's Sherlock?"

John frowned and glanced back to Mrs Hudson, who was standing by the fireplace with one hand nervously supporting her chin. "He's here. Why are you?"

His tone was polite enough, but he hadn't moved, nor had he opened the door any further; his posture was stiff and straight-backed, chin raised, hands looking as though they wanted to clench but were being forcibly prevented from doing so. Defensive, a military man's response, but the question was – defence of or against what? This could be a reaction to Mycroft's unexpected presence, or to whatever state Sherlock was currently in.

The flash of analysis passed though Mycroft's thoughts in less than a second. "Here," he repeated. "Where?"

"He's – in his room," the doctor answered slowly. "I don't – why are you asking?"

Mycroft drew in a soft, sharp breath. "Alone?"

The sudden flicker of realisation in John's widening eyes was enough; Mycroft did not need either the nod or the stammer of concern that followed to goad him into immediate movement. Eyes hard, he quickly pushed past the doctor, crossing the sitting room in a few long strides and the hallway in another four or five. At Sherlock's room, he set his arm against the door and shoved, and was quite surprised when it swung inward with no sign of resistance.

For one anxious second, Mycroft thought that he might already have arrived too late; his gaze snapped to the bed, where his brother was lying flat on his back, unmoving and staring without expression up at the ceiling. There were no lights on, and Sherlock's natural pallor seemed even more pronounced in the glow spilling from the open doorway. Mycroft took a step forward.

"It was Lestrade, wasn't it?"

Mycroft stopped. Sherlock's voice was, thankfully, quick and completely coherent, but there was an underlying tension to it that sent warning signals flashing like strobe lights through his mind. Lestrade had been right to worry.

"It's hardly relevant at this point," he answered softly, as his gaze roamed quickly over Sherlock and then moved to take in the room at large. There was nothing in view – a fact that, rather than setting him at ease, only served to heighten his concern. "But yes; it was."

A muttered breath that sounded very much like a swear came from Sherlock's direction, even though his lips had not appeared to move at all.

"Was what?"

Sherlock sat up very quickly. The heads of both brothers swivelled around, one regarding John with slight exasperation, the other with an expression that mingled surprise and resentment together in one dark glance. From his position in the doorway, John looked from Sherlock to Mycroft as though he was beginning to understand exactly what this was all about, and was hoping against hope that his suspicions would be proved wrong at any moment. Mycroft wished he could have done just that, but, unfortunately, he knew his brother far too well.

"I came here at the – _request_ – of Detective Inspector Lestrade," he explained quietly, keeping one eye on Sherlock even as he slipped further into room. "He was, shall we say, concerned about my brother's state of mind after the events at the Hungerford Bridge earlier this evening."

John's eyes widened, then narrowed. "How did you – "

"Not now."

Mycroft cut him off with a sharp gesture and an even sharper tone, for out of the corner of his eye, he could see his brother's face growing steadily darker at this unwelcome intrusion. There would be time to explain everything to Doctor Watson – _after. _After he checked. After he looked thoroughly in, through, behind, and under everything in this room. It was, unfortunately, a process he had become rather adept at over the years, despite the fact that Sherlock, who was perfectly aware each time of what would happen, kept trying to find (or create) new hiding places that he somehow thought his brother would miss. Their minds were too similar, however, and Mycroft very, very rarely found it necessary to make a second visit.

In point of fact, he wasn't at all pleased to be making a first visit in this case. It had been a long time since he'd been manoeuvred into a position where he had to clarify the exact relationship that Sherlock had with narcotics. Five years, he thought, with a slight compression of his lips. Lestrade had been a godsend. Whether John Watson would prove equally capable remained to be seen.

"Doctor Watson," Mycroft instructed evenly, "kindly keep my brother where he is. I doubt that force will be necessary, but expediency does tend to be relative. As long as he _stays put_."

His last words blurred the line between implication and blatant threat, and whether it was that or the result of the doctor's own observations and conclusions, John seemed to understand. He crossed the two or three steps between the door and the bed and then, to Mycroft's unconcealed surprise, put an unshaking hand on Sherlock's shoulder. Sherlock tried, more than a little irritably, to pull away, but it was apparently more difficult than it appeared to shake away the steady grip of an army doctor. Mycroft allowed himself a soft breath of relief that he made sure neither of them saw.

He then proceeded, quietly, precisely, and methodically, to turn Sherlock's room inside out.

The familiarity of the process was in no way comforting; Mycroft could hardly suppress a grimace of mingled exasperation and disappointment as he folded back clothes, sifted through the contents of drawers, ran experienced fingers over the front, back, and sides of various objects of furniture and decoration. Even the framed print of the periodic table and the models on the shelves in the far corner did not evade his attention, and he had just begun to entertain the faintest speculation that perhaps there was nothing here, after all, when his fingertips found a miniscule catch at the back edge of one of the shelves. He sighed and looked around, meeting his brother's gaze steadily.

"A false panel? Tiresomely uninventive, Sherlock." He turned back and shifted a few thick books out of the way.

"Mycroft – "

"Sherlock."

"Mycroft," his brother said again, "if you even – "

He broke off, but his tone caused Mycroft to twist around again. He found in Sherlock's features what he had expected to find – anger, tension, resentment bordering on hatred – but what he had not anticipated was the flicker of entreaty that passed like the briefest ghostly image across the surface of his brother's eyes. Mycroft went very still for a moment, watching, and as his own glance shifted to Doctor Watson, he suddenly understood.

John did not know, only suspected. And Sherlock, in his infinite unpredictability, did not _want_ him to know.

It was a request that Mycroft could not grant. Wordlessly, he turned away, and when a minute later he pulled out the contents of the hidden spot and he saw a spasm of raw emotion contort his brother's face, he pretended not to notice.

"We'll go in the other room," he told a slightly shocked John Watson, who was standing in that same position with a look of pained disappointment growing steadily in his eyes. "Mrs Hudson can stay with him for now; it seems we need to talk."

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**Yup, looks like this is going to be a three-part story! Unexpected, to say the least. Please let me know your thoughts! :)**


	3. Part III: Choice

**Author's Note: **And here it is, the third and final installment to the story that was never meant to be more than a oneshot in the first place. I do believe the conclusion is fitting, and I hope you all do, as well!

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_Part III: Choice_

They found Mrs Hudson hovering just outside the door, leaning one shoulder against the wall and wringing her hands in front of her, an expression of distress adding further wrinkles to her already-lined features. It was obvious that she had heard most, if not everything, that had transpired, and the thought was causing her no little measure of anxiety. Mycroft let out a soft breath and willed himself to pause his stride; it was likely, after all, that the woman would have to cope with many more nights like this one, especially if Doctor Watson happened to be absent, and for that, if nothing else, he owed her at least a word or two of reassurance, however paltry.

"I presume you have at least a vague notion of the current situation, Mrs Hudson," he said, looking squarely down at her, and if his voice was rather frosty, he hardly thought anyone could blame him for that.

She nodded, twisting her fingers together as though she were trying to knot them into rope. "He's in a bad way, isn't he?" she asked softly, with a betraying glance toward the doorway, where John, thorough man that he was, had remained to keep a careful vigil until someone else could take his place.

"To put it delicately, yes."

Mycroft hesitated and closed his eyes for a brief moment, but he had had far too much experience in the handling of fragile conversations to even think of putting off further explanations. Sherlock really did drive him to it. He lifted his chin slightly.

"If you weren't already aware, Mrs Hudson, I feel obliged to inform you that my brother has an unsavoury dependence on certain substances, narcotics in particular. While you may have noticed that nicotine is his drug of choice, there have been and likely will be times in the future when this is not enough, in which case, cocaine and morphine appear to be his greatest preferences. I take it you are in complete agreement when I say the latter two are to be avoided or prevented if at all possible."

She let out a soft noise of dismay, bringing one clenched hand up to her mouth and looking alternately between Mycroft and John as though waiting for a contradiction from one of them. "Oh, I know he used to smoke – nasty habit, I won't even allow it in here most times – and then he puts those things, those patches, on his arms a lot these days – says it helps him think – and I don't – "

"Well," Mycroft said, cutting her off, "this is rather more serious than that, isn't it?"

It was a rhetorical question; he gave her no chance to respond, but turned his head back to John and gave the doctor a short, crisp nod. "If you wouldn't mind, Doctor Watson" – and he gestured pointedly in the direction of the sitting room. "Mrs Hudson will keep an eye on him until we're finished."

All the same, he did not miss the hesitation with which John complied, the way his hand stuck to the doorway as long as possible before falling with visible reluctance back to his side. He did not want to leave Sherlock. Understandable, to some extent, but at the moment, what Mycroft had to say was far more important than anything the doctor could possibly hope to accomplish by staying in Sherlock's immediate vicinity. With so many people up against him, the danger was past – for now.

Doctor Watson put a gentle hand on Mrs Hudson's shoulder as he turned away, murmuring a soft "Thanks" before she scuttled quietly into Sherlock's bedroom. Mycroft said nothing until they had reached the sitting room again, but found to his surprise that when he did open his mouth to begin, John had already made the first strike.

"No one told me about this. Bothered, even."

His voice was unexpectedly cold, and not for the first time, Mycroft found himself wondering how far the unknown depths of this man extended. He prided himself on his ability to read an individual at a glance, but John Watson seemed to defy definition.

"Surely you had your suspicions," he responded evenly, folding his hands neatly behind his back. "Sherlock can be terribly unsubtle about some things, and I'm afraid this is one of them. Well, you're a doctor. You know the signs."

"Maybe," John conceded flatly, in a harsh, unfriendly manner that was hardly a concession at all, "but there haven't been any, not recent ones. He hasn't done anything – hasn't even smoked – just the nicotine patches when he's on a case."

Mycroft considered for a moment before answering slowly, "It has been... quite a while. I had foolishly begun to hope that he had made a change for the better, and that any warning I might give you would be, shall we say, pre-emptive in the extreme." He breathed a low sigh, focussing carefully on the rug beneath his feet before flicking a sincerely apologetic glance upward. "You have my apologies for that, Doctor. An error in judgement, on my part."

"Damn right," John muttered.

The doctor folded his arms over his chest and stared steadily, almost disconcertingly, at Mycroft for rather a long time, in a way that suggested he would very much like to kick the elder Holmes out of the flat right there and then and was only refraining from doing so because there was information he needed to know. Mycroft kept his composure, and waited.

"So." John's tone had hardly changed at all. "What's going on, then? How bad is it? How often does it happen – and what the hell do you expect me to do about it?"

"Beginning with your last question, I think you know perfectly well what you _have_ to do about it." Mycroft's voice became suddenly sharper, more insistent, though he was beginning to doubt that an air of authority would have anything less than a detrimental effect on the much-needed cooperation of John Watson. Soldier he might be, but ordinary he was not; that much Mycroft had discovered during their first meeting. "Tonight," he went on, "you have to watch him, you have to stay with him; and from now on, Doctor Watson, you have to be aware that certain extremes will push Sherlock past the point of his own discipline, and when that happens, you have to be ready to act accordingly. My brother is a man of volatile temperament, as you've already had occasion to notice, and he is very much a danger to himself in these cases."

"Yeah, really? Never would've guessed."

"I would advise you _not_ to waste your scorn on me, Doctor," Mycroft told him sharply, with the uncomfortable feeling that underneath the exterior he had spent so many painstaking years polishing, he was not nearly as immune as he would have liked to the subtle stirrings of guilt and disappointment. "Whether or not I deserve it isn't really the issue at hand."

Doctor Watson's mouth had compressed to a thin, hard line, and despite the soft orange light of the lamps in the flat, the shadows under his eyes seemed even more pronounced than ever. "Answer the rest of my questions, then," he said quietly.

"It's difficult to say. For all his logic and his carefully-calculated solutions to life's more obscure problems, my brother is hardly a machine." Mycroft rubbed two fingers over his temple in a futile attempt to relieve the headache that was building there. "It's not always easy to tell how certain – incidents – will affect him; failure, of course, is the most likely."

"You mean like today. At the bridge."

Mycroft nodded. "Sherlock is in constant need of mental stimulus. When he can't get it, or when it is cut off too soon, too suddenly, he resorts to more artificial methods to make up the difference."

"And when he's solved something too late – "

"Exactly."

They stood there in uncomfortable silence for nearly a minute, each, Mycroft presumed, occupied with his own dark thoughts. There was very little he could do to try to soften the blow, but he seriously doubted whether blunting such an inevitable if unpleasant reality might not have the opposite effect, in the end. He wasn't about to risk testing that theory.

"You know," John remarked quietly after a long interval, "the way you explain all that, it just sounds like he's doing it because – because he can't stand to be proven wrong. Like he doesn't want to admit it, so he just doesn't – "

But already Mycroft was shaking his head. "It's far more complex than that, I'm afraid, and nothing I care to delve too much into at the moment. But I think you'll come to see it, in your own time." He turned, paused, and then looked slowly around again to fix the doctor with a pointed, searching glance.

"Always assuming, of course, that you choose to stay. You are under no contract, Doctor Watson. No contract except your own."

He spoke the literal truth, in what he meant to be fair warning, for he knew through painful personal experience that Sherlock was no easy man to live with, even drugs aside. It took a man of a certain character to merely put up with him – someone like Inspector Lestrade – and someone with something even more, something strong and oddly intangible, to take any step further than that.

One month later, when a Chinese smuggling ring seeped into the open in search of a jade hairpin, John Watson was still there.

A month and a half later, when the man known as James Moriarty began his deadly game with the brilliant detective Sherlock Holmes, John Watson was still there.

And ten months later, on a very dark and aching Christmas night, when Sherlock Holmes returned to his flat with the smoke of one cigarette still burning in his lungs and a pale, haunted look he only managed to partially conceal flickering in his eyes, John Watson was still there.

"You have to stay with him, John."

And John Watson stayed.

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**Thank you! Thank you so much to all those who have favourited, followed, and especially to those who have reviewed (of course, you still have one more to do! ) I've enjoyed writing this very much indeed. Any final and/or overall comments you could leave would just make my day or night or whenever I happen to get them. :) **

**In a shameless bit of prompting, I would also encourage any and all of you lovely readers out there to take a look at a post-Reichenbach, multi-chapter story that I'm currently working on in collaboration with the ever-brilliant Setep Ka Tawy. It is "Returning to Tomorrow", and can be found on Setep's profile. Heavily plot-based, the story deals with not only Sherlock's return (which is, I assure you, probably not quite as you've read it before) but with an intricate scheme devised by someone we all know rather well. Please take a look, if you've a mind!**

**Again, your thoughts on this piece have meant so much to me, and thank you for being wonderful readers!**


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